Ophthalmic lenses are normally manufactured by a mechanical process in which a block of polymethylmethacrylate (PMMA) is machined while being adhesively held on a support. The machining is quite difficult because of the small size of the lens and the intricacy of the shape into which the lens must be machined.
Typically, three operations must be performed to shape a lens:
(1) the workpiece must be cut out from a blank to form, e.g., an integral optic and haptic;
(2) the surface of the workpiece must be machined to the desired optical specifications (which may include convexities or concavities of varying radii at different points on the surface of the lens; and
(3) the edges of the workpiece must be radiused or rounded.
In the prior art, the edge rounding step alone typically required 7-14 days of gemstone tumbling, and precision was hard to accomplish in all of the steps.